BACKGROUND: Evidence suggests that neither the standard-dose nor high-dose influenza vaccines are effective among patients with end-stage renal disease (ESRD). A second, booster dose of standard-dose vaccine may provide better protection than a single dose, but it is unknown whether a booster dose is used in clinical practice.
OBJECTIVES: To compare baseline characteristics of patients with ESRD who receive one versus two doses of influenza vaccine in a given influenza season, overall and by influenza season.
METHODS: Patients with ESRD receiving hemodialysis were identified in the United States Renal Data System during each influenza season from 2010 to 2016. Patients were eligible for multiple seasons. Standard-dose vaccines of any type were identified between August 1 and the end of the influenza season, except for the season starting in 2016, where the data ended on December 31. Baseline demographics were assessed on the date of the first vaccination date. Healthcare utilization measures were assessed during the 30 days before the first vaccination date. We compared patient characteristics of one vs. two-dose recipients using a standardized mean difference (SMD).
RESULTS: Of 1,076,535 influenza vaccine recipients, 2.2% received at least two doses of standard-dose vaccine during a single influenza season. This proportion was similar for all influenza seasons. There was little difference between patients with one and two doses with regards to demographics. However, two-dose recipients were more likely to be dual-eligible for Medicaid than one-dose recipients (64% versus 51%; SMD = 0.26). Similarly, two-dose recipients had a higher prevalence of skilled nursing facility stays in the 30 days prior to the vaccination date (10% versus 4%, SMD = 0.26). The pattern was similar for hospitalization days. Vaccination was administered more often in the outpatient setting than in the dialysis clinic, regardless of dose. Among two-dose recipients who received the first dose in the dialysis clinic, 85% received the second dose in an alternate setting.
CONCLUSIONS: A small proportion (~2%) of vaccinated patients received two doses in one influenza season. Some patients received the second dose in a different setting from the first, perhaps in part due to an inability to transfer medical history data across health care facilities resulting in inadvertent re-vaccination, or a true perceived need for a booster dose. Investigating the effectiveness of a two-dose vaccination strategy could be possible if differences in health care utilization can be addressed in the analysis.
